Tonepad DS-1 Not making any sound :-( Bypass works.. pic included

[Hav]

If you are reading 8.9V on Pin 4 of the IC when it is removed.... YOU HAVE A SHORT BETWEEN V+ (9VDC) and GND SOMEWHERE!

Remove power from the circuit and remove the IC. Put the DMM black lead on the Pin 4 spot. Put the red lead on the Pin 8 spot. Tell me how many ohms you are reading.

I am willing to bet it is less than 50 

Somewhere you have a short and need to locate it 

EDIT: Quick tip.... check to make sure you wired your Input jack correctly for battery shut off..... if you are using a battery 

yep your right! I definitely have less than 50! its at 0!!! if i set it too '200m' on DMM i get 0.02!!

Where else can this short be? can it be a dodgy switch / wrong way round transistors?

oops, ohms being resistance lol - yep is 19.2 

[Govmnt_Lacky]

Pics of the ENTIRE board (component side, trace side, and offboard wiring) will help a lot.

Also... is this circuit OUTSIDE of the enclosure?

[Hav]

yes circuit is outside enclosure... ok will get some pics up...

[Hav]

Ok here are some more pics:

http://havsingh.com/Guitar/DS1/Ref%20Files/

Hope they are good enough, if you need others please let me know!

[Mike Burgundy]

Warning: There's at least 3 problems.
1) pin 4 is not (well) connected to ground, or it wouldn't be able to lift up to  (almost)9V. It should be dead shorted to ground.
2) pin 4 is, as found, somehow shorted to 9V.
3) Vref is wrong somehow. it should be at half supply voltage, but it is also at full voltage - pin 3 is connected to Vref, but showing (almost) 9V.

After that is sorted, it may well be the transistors bias up nicely. If not, time to dig deeper.

[Hav]

yep I just can't find how its shorting... i literally cannot see any shorts whatsoever. although its clearly there somewhere lol. can it just be a dud IC socket? can you even get dud IC sockets ?

Also, DPDT says 1, 2, 3 on one side. I totally didnt see that before.. related? I just thought these things can go either way (as long as its like this:

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[Govmnt_Lacky]

Your DPDT looks good.

I recommend taking an xacto knife and using it to isolate the entire +9V trace from the rest of the circuit. What I mean is that you "scratch" between the entire 9V trace and any other nearby traces for the entire length. This way... even if there is a micro short... you will break it.

If that doesn't work, I would check(On the COMPONENT side) that every point that is supposed to connect to Ground is connected. Make sure they are shorted. This will check for cold solder joints.

Report back if none of this works and..........

Good Luck 

[Hav]

Ah thanks I will give this a try! By '..connect to ground is connected ..shorted' how do I do this exactly?

[Hav]

OH MY! I don't feel silly...

Plugged Jack in to input and voltages completely changed. Note to self.. DAMN IT :-s

Anyhow, so now voltages look better, but still no sound. The only thing that looks off its Q2.

Here are some figures:

Battery 8.8

IC
4.4     8.8
4.4     4.3
3.8     4.4
0        4.4

Q1
E
3.3     2.7      8.8

Q2
E
0        0.6       0.9

Q3
E
2.9      1.9        8.8

now to battle this No Sound problem? Q2 doesnt look right, swapped Q3 with Q2 and got the same figures so I assume they are functioning correctly... ?

again, I can hear volume tone and gain increase and decrease. Bypass works. just no engaged sound...

[GibsonGM]

From the looks of it, Q2 is not getting power, which should be near 9V.   

Q1 and Q3 are screwy in that your emitters are more positive than base, which is 'not possible' (at least in order to function, ha ha).    E should be about .5 to .7v lower than the base - see how it's .6 lower on Q2?

Take this a step at a time...you need to find out why your emitter at Q1 is more positive than base, and then trace back from collector of Q2 and see why no power...take it a step at a time.  Hopefully there will be one problem that, when corrected, will take you up to the IC.  Maybe.

I suspect a bad component VALUE somewhere in that area....too high of a resistor or something that was accidentally installed rather than the right value....your Vref looks good at the IC, anyway, so let's find out why it's not near 4.5V at Q1's base....you should get Vref at the base of Q1, GND after the emitter resistor, and ~9V on the collector.  Once that's set, we'll move to Q2!  Short or part value....track it down! 

[Hav]

Thanks Mike!

I will get on this tonight, but before I do,

just want to confirm that I have these Transistors in the right way:

Datasheet: https://www.fairchildsemi.com/ds/MM/MMBT5089.pdf vs my layout on the first post...

I think I have it right, but last time I thought I had it right and was totally wrong (apparently these pinouts don't mean much).

[Hav]

Right, so yep, found a 22R instead if 2M2 (bottom left of the image in first post). !!!!

Thats given me a distorted sound.

The Qs still gave the same readings, so I thought lets just flip em round (i'm finding different pinouts for the same transistor!!)

Now, I assume its correct:

Q1

E
0.68     1.15      8.88

Q2

E
0          0.6         5.29

Q3

E
0.35        0.88     8.88

do these look about right?

[Govmnt_Lacky]

do these look about right?

Is the pedal working? 

[Hav]

well yep suppose it is lol! that '0' is just making me think. but

THANKS EVERYONE! :-) now to box! :-)

[GibsonGM]

Great!   The voltages look very nice from here     Glad you were able to get it going!!